<html>
<head>
<style type="text/css">

body { font-family: monospace; width: 4ch; }
body::first-line { }
body *::before { content: 'w';}

</style>

<script type="text/javascript">

function boom()
{
  var de = document.documentElement;
  var body = document.body;

  var span = document.createElementNS("http://www.w3.org/1999/xhtml", "span");
  var r1 = document.createElementNS("http://www.w3.org/1998/Math/MathML", "mrow");
  var mmm = document.createElementNS("http://www.w3.org/1998/Math/MathML", "mmultiscripts");

  body.appendChild(span);
  r1.appendChild(document.createElementNS("http://www.w3.org/1998/Math/MathML", "mrow"));
  body.appendChild(r1);
  body.appendChild(mmm);
  de.offsetHeight;
  r1.appendChild(document.createElementNS("http://www.w3.org/1998/Math/MathML", 'mrow'));
  de.offsetHeight;
  mmm.appendChild(document.createElementNS("http://www.w3.org/1998/Math/MathML", 'mrow'));
  de.offsetHeight;
}

window.addEventListener("load", boom, false);

</script>
</head>
<body></body>
</html>
